1. Field of the Invention
The present invention relates, in general, to a frequency control circuit, and, more particularly, to a receiver and circuit for generating a frequency control signal and method of generating a frequency control signal.
This is a counterpart of and claims priority to Japanese patent application Ser. No. 173857/2002, filed on Jun. 14, 2002, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
A conventional receiver has only one phase difference operation circuit and an integration circuit. By the way, the conventional receiver must satisfy the following two requirements to generate a signal having a stable frequency. The first is that when a carrier difference (phase difference is larger than a threshold value, the integration circuit is supplied with a large value causing the carrier difference to be converged. The second is that when the carrier difference approaches the convergence, the integration circuit is supplied with a small value. To satisfy the above requirements, the integration circuit in the conventional receiver is supplied with a phase difference which is generated by the phase difference operation circuit, multiplied by a loop gain value.
However, the conventional loop gain value is merely generated by an unreliable control, for example, time control. Therefore, the conventional receiver lacks stability.